Chassis for inverter

ABSTRACT

The present invention provides an inverter or other electronically controlled power source for transforming electrical energy into electrical energy of predetermined voltage and/or current comprising: an inner housing for housing the main circuitry of the inverter, a cover connected to the inner housing, covering at least part of the inner housing, defining at least one cover channel between the inner housing and the cover for air to flow through that channel for cooling of the inverter, whereby the cover channel is adapted to facilitate natural convection of the air. The present invention further proposes an inverter according to any of the preceding claims, additionally comprising at least one ventilator to enhance an air flow through the channel. According to the invention the cooling properties of an inverter are to be improved.

FIELD OF THE INVENTION

The invention relates to an inverter or other electronically controlledpower source for transforming electrical energy of predefined voltageand/or current. Further, the invention relates to a method for settingup and operating an inverter or other electronically controlled powersource.

STATE OF THE ART

Inverter and other electronically controlled power sources fortransforming electrical energy of predefined voltage and/or current aregenerally known. Such inverters are generally known and used to provideelectrical energy of predefined voltage and/or current. To give oneexample, such inverters are used to transform electrical DC-energyprovided by a solar generator into a basically sinusoidal current signalfor feeding into a public or private grid. E.g. a 60 Hz signal for thepublic grid in the United States or a 50 Hz signal for the publicEuropean grid.

For transforming the electrical energy at least some power loss withinthe inverter is unavoidable. In particular such power loss appears atsemiconductor switching elements such as IGBTs and also at chokes. Toavoid malfunction of the inverter, in particular of the lossy componentsat which the power loss basically appears, cooling is necessary to avoidexceeding of a certain temperature.

Additionally, the inverter might not only suffer from heat generated bythe electronic or electrical components but also by the sun. Inparticular if the inverter is used in connection with a solar generator,a high level of radiation of the sun is expected. This results in adilemma for the designer of the inverter. I.e. the inverter could beisolated against heating of the sun but on the other hand an isolationmight also make dissipating of heat more difficult.

However, it is also one general demand for an inverter to be sealedagainst water and dust and the like to protect the inverter. From theGerman utility model DE 20 2004 009 926 U1 an inverter is knowncomprising two chambers. These two chambers are separated by one wallthat comprises the lossy components. One chamber comprises a coolingaggregate and each lossy component or a heat sink of it is attacheddirectly to the separating wall and facing the chamber of the coolingaggregate.

However, such a common wall providing the lossy components might conductheat from a lossy component to its heat sink, but it also conducts heatin the reverse direction, i.e. from the chamber comprising the coolingaggregate to the chamber comprising the other electronic components,which are not considered to be lossy but still may not get too hot.Also, the success of cooling basically depends on the efficiency of thecooling aggregate. Therefore, the success also depends on the energyprovided for the cooling aggregate. Such an inverter does also not solvethe dilemma of protection of the inverter against the heat of the sunand simultaneously still being able of dissipating heat generated withinthe inverter.

OBJECT OF THE INVENTION

Accordingly it is at least one object of the invention to provide aninverter which reduces at least one of the above problems and to providea method of setting up and/or operating such an inverter. In particular,it is one object of the invention to improve the capabilities of aninverter regarding dissipating of heat and protection against heat. Afurther object of the present invention is to improve the efficiency ofthe inverter regarding the dissipating of generated heat and protectionagainst heat from outside.

To achieve these and other objects the invention proposes an inverter orother electronically controlled power source for transforming electricalenergy into electrical energy of predetermined voltage and/or currentcomprising: an inner housing for housing the main circuitry of theinverter, and a cover connected to the inner housing, covering at leastpart of the inner housing, defining at least one cover channel betweenthe inner housing and the cover for air to flow through that channel forcooling of the inverter, whereby the cover channel is adapted tofacilitate natural convection of the air.

Accordingly, the invention proposes an inverter having an inner housingfor housing the main circuitry of the inverter. Of course, if anotherelectronically controlled power source is used, the inner housingcomprises the main circuitry of that other power source. Such maincircuitry usually comprises of one main circuit board having the most oreven all electronic components attached, either directly or by means offurther smaller circuit boards. Only special parts of the inverter thatare necessarily or at least usually located outside might not be housedin the inner housing, such as an operating panel or a display. Also, achoke which is used for filtering our smoothing the generated current orother component dissipating high amount of energy might not be insidethis inner housing.

A cover is connected to this inner housing, covering at least part ofthe inner housing, defining at least one cover channel between the innerhousing and the cover. Such cover channel is designed as an air channelfor air to flow through this channel to cool the inverter, provided thatthe air is cooler than the inverter. The channel is provided such, thatnatural convection of the air is facilitated.

Natural convection of air takes place according to warmer air ascendingin an environment of cooler air. The force of such natural convectionis, compared to an airflow generated by a fan or a vent, usually weak.The channel to facilitate natural convection must therefore comprise arelatively large cross sectional area. Of course, such channel must beof generally vertical orientation to let the warmer airflow upwards.

The vertical orientation of the channel is provided when the inverter isin use and accordingly, this vertical orientation assumes that theinverter is arranged in a normal upright operational position. Such anupright operational position is usually indicated at the inverter. Inparticular, any printing or even signs indicate an upright position,including any letters, numbers or signs displayed in a display of theinverter.

According to a further aspect of the present invention the cover isadapted to protect the inner housing against sunlight, in particularagainst direct radiation of sunlight. Accordingly, the cover is designedand attached to the inner housing such, that the sunrays do not or onlyin a very small measure reach the inner housing. I.e. it is onlynecessary, that the cover basically provides a shade for the innerhousing but the cover does not necessarily have to enclose the innerhousing completely. However, it must be noted, that the protectionagainst the sun should be provided for a complete day and thus thechange of the direction of the sun over the daytime must be taken intoaccount.

According to one embodiment the cover comprises an outside having alight color, in particular white or silver. Such light color enhancesthe protection of the cover against radiation of sun light. The colorcan be provided in several ways such as a painting or a coating. Inparticular when the color is silver, it can be the natural color of ametal such as aluminium forming the cover.

Advantageously, the cover covers at least two sides of the inner housingpreferably at least three sides and in particular five of six sides ofthe inner housing. The number of sides of the housing to be covereddepends on many aspects as the shape and size of the inner housing, theshape and size of the cover and also on the intended use and location ofuse of the inverter. Considering an inner housing having a basicallycuboid like shape and thus six sides, at least two, usually three sideswould be reached by the sun during a (cloudless) day. These sides shouldbe covered by the cover. In particular, three vertically arranged sidesof such inner housing should be covered, also resulting in at least onevertical covered channel. If such cover covering three verticallyarranged sides of the inner housing also touches two edges of thesethree sides, three separately covered channels may result, eachcorresponding to one side. However, it is preferred that the covertouches the inner housing only as far as necessary for attaching thecover at the inner housing, to avoid any unnecessary heat bridges.

According to one aspect the invention, the cover covers five of sixsides of the inner housing i.e. only the back side of the inner housingis not covered by the cover.

A further advantage of such cover is to provide a possibility of anindependent appearance. Generally the appearance of the inverter isdependent on the cover rather than the inner housing and any smallchanges in variations of the inverter might change the appearance of theinner housing, but the cover and thus the appearance of the inverter mayremain unchanged.

For protection against the sun, in particular against direct radiationof the sun, the cover would not transmit but reflect the sun. However,at least some heating of the cover when exposed to the sun is expected.The heated cover will as a result heat the air in the cover channel andthus will result in natural convection of the air in the cover channelor it will enhanced it. As a further result there will be an air streamin upward direction, sucking in cooler air at a bottom and this willenhance cooling of the inverter. In other words, heating of the cover bythe sun will result in a cooling effect.

According to a further invention a choke or other component dissipatinghigh amount of energy of the inverter is positioned in the cover channelsuch, that air in the cover channel transports heat from the choke orcorresponding component and heat of the choke or corresponding componentenhances convection of air in the channel. Accordingly, a choke orcorresponding component is positioned outside the inner housing in thecover channel and is exposed to an airflow in this channel. The air willflow along the choke or corresponding component resulting in cooling thechoke or corresponding component respectively and heating the air. Sincethe air gets warmer, natural convection and thus the flow of air in anupward direction is enhanced, improving the cooling of the inverter andthe choke or corresponding component. Further embodiments and advantagesdescribed for a choke apply also to an other component dissipating highamount of energy.

According to one aspect of the invention the choke or other componentdissipating a high amount of energy is positioned at the top or at thebottom of the inner housing and thus is arranged in a top area of thecover channel or a bottom area of the cover channel respectively. If twoor more chokes are used, at least one could be arranged in the top areaand at least one other could be arranged in the bottom area.

According to one aspect of the invention, the cover channel comprises aninput opening for air to enter the cover channel and an output openingfor air to exit the cover channel and whereby the input opening isarranged at the bottom of the inverter and the output opening isarranged at the top of the inverter. Such top arrangement and bottomarrangement is to be understood with respect to an inverter beingarranged in a normal upright operational position. If a choke ispositioned in a bottom area, this would preferably be close to the inputopening and if a choke is arranged in the top area this could preferablybe close to the output opening. If a choke is arranged close to theinput opening, it will be subjected to cool air entering the coverchannel resulting in a good cooling result of the choke. On the otherhand, if the choke is arranged close to the output opening the airheated by the choke will subsequently exit the cover channel and thuscannot heat the inverter.

According to a further aspect the inverter comprises at least one heatsink for cooling power components of the inverter, whereby the heat sinkis attached to the inner housing basically providing a space between theheat sink and the inner housing.

Such a heat sink usually consists of a base with one or more flatsurfaces and an array of comb or fin-like protrusions to increase theheat sink's surface area contacting the air. Contrary to known systemsthe base does not provide one wall of the inner housing nor is the baseand in particular such a flat surface directly connected to a wallhaving a large contact area. Instead, the invention proposes to leave aspace such as a gap between the heat sink and the inner housing, inparticular between the base or base plate of the heat sink and a wall ofthe inner housing. This way, it is avoided that heat in the heat sink isconducted back to such wall of the inner housing and thus back to theinner housing. Accordingly this avoids any reversely directed flow ofheat back into the housing. This aspect shall improve the coolingproperties of the inverter with respect to the heat sink. This aspectmay improve the heating properties of an inverter independently to theaspect of providing a cover to further provide a cover channel. However,both of these general features may be combined having synergeticeffects.

According to one aspect of the invention the inner housing is sealedagainst the environment to prevent the circuitry of the inverter againstdust and/or water. This way, a good protection can protect the circuitryof the inverter by means of a sealed inner housing, whereby good coolingproperties can still be achieved.

According to a further embodiment power components which need externalcooling, e.g. semiconductor switches such as IGBTs, or other componentsdissipating a high amount of energy extend through the casing of theinner housing against the heat sink and/or are sealed against the innerhousing. Accordingly, such power components may be attached to the samecircuit board as all other components which do not need cooling. Butthese power components extend through the casing of the inner housing,in particular through a wail of inner housing, extend through the spaceor gap between the inner housing and the heat sink and finally areattached against the heat sink e.g. at a base or base plate of it. Thisway the power components are mounted at the heat sink for conductingheat generated in the power components to the heat sink but the innerhousing remains sealed and a distance between the inner housing and theheat sink does also remain.

Advantageously the heat sink comprises a base plate having one or aplurality of power components attached to that base plate, whereby thebase plate comprises protrusions extending towards the power componentsso as to provide a base for each attached power component. Suchprotrusion can extend at least partly through a gap or space between thebase plate and the inner housing. This way even flat componentselectrically connected within the inner housing can be attached to thebase plate and a gap or space can still be provided between the baseplate and the inner housing. According to one embodiment, at least oneof such protrusions can extend through the gap or space into the housingfor being attached to a component that needs cooling, whereby theprotrusion is sealed against the wall of the inner housing. Therefore,the protrusion can conduct heat of that component to the base plate ofthe heat sink, whereas conducting heat from the base plate back to theinner housing is avoided due to the gap or space between the base plate.

As proposed according to one aspect the heat sink may be attached to theinner housing by means of distance pieces. E.g. the heat sink might bescrewed at four corners of the heat sink through such distance piecesand into the inner housing. Such distance pieces might be provided ascylinders of a material that does not conduct heat very well, such as aplastic material, or a ceramic material or resin or such alike. Thedistance pieces may also take the form of two bars holding the heat sinkat two sides.

It is also to be noted, that at least one main circuit board in theinner housing does not necessarily need to be attached to a wall of theinner housing facing towards the heat sink, but there might also beprovided a gap between such circuit board and the wall of the innerhousing, to have a further distance providing a further heat protectionof the circuit board.

In a further embodiment the inverter comprises a heat sink channelaccommodating the heat sink for guiding air long the heat sink forcooling this way, providing an air stream along the heat sink isfacilitated. If the heat sink comprises a plurality of fin-likeprotrusions, the heat sink channel is oriented in the same direction asthe fin-like protrusions are.

According to one embodiment an airflow along the heat sink is enhancedby means of at least one vent for blowing air through the heat sinkchannel along the heat sink and in particular also through the space orgap between the inner housing and the heat sink. This way, the heat sinkchannel ensures a certain direction of an airflow whereas the ventprovides for or increases the velocity of such air stream. As the heatsink is basically not attached with the large surface of a base of it tothe inner housing, this surface of the base can also be used fordissipating heat by means of an air stream. Therefore, the vent not onlyblows the air along the finlike protrusions but also along such surfacefacing the inner housing and thus facing the space or gap between them.

According to a further aspect it is proposed to provide the outputopening of the cover channel adjacent to an output opening of the heatsink channel. This way, the hot air coming out of both output openingsmay be directed in the same direction. Even though the cover channel andthe heat sink channel are basically independent of each other thearrangement of both openings next to each other might result in asuction effect from the one channel to the other one. In particular, ifthe heat sink channel is provided with at least one a vent whereas thecover channel is not provided with a vent the air of the heat sinkchannel might flow with a higher velocity and thus the cover channelmight be subjected to a suction effect resulting from the highervelocity of the heat sink channel.

The invention also provides for a method for setting up and operating aninverter or other electronically controlled power source fortransforming electrical energy into electrical energy of predeterminedvoltage and/or current, having an inner housing for housing the maincircuitry of the inverter and a cover, covering at least part of theinner housing, defining at least one cover channel between the innerhousing and the cover comprising the steps:

-   -   attaching the inverter on an object such as a wall to hold the        inverter and    -   arranging the cover channel in a basically vertical manner, such        that an input opening for air to enter the channel is basically        arranged at the bottom of the channel and an output opening for        air to exit the channel is basically arranged at the top of the        channel.

Additionally, the method comprises the step:

-   -   positioning the inverter such, that the cover basically faces        the direction to the sun at day time such, that the cover at        least partly protects the inner housing of the inverter against        radiation of the sun at day time.

Accordingly, one step is to arrange the inverter in a fixed position andthus in an upright position. For protection against radiation of the sunthe inverter is positioned such, that the cover basically faces thedirection to the sun at daytime, taking into account, that the directionof the sun will change of approximately 180° during the daytime. Theterm “facing the direction of the sun” basically refers to a directionin the horizontal plane, and is not meant to refer to an inclination. Asa result of providing an upright position of the inverter the coverchannel should also be arranged in a basically vertical manner. Theoperating of the inverter with respect to transforming the electricalenergy into electrical energy of predefined voltage and/or current isperformed as generally known. However, it should be taken care, that anyopenings of the cover channel and/or the heat sink channel are kept opento prevent the air to flow in the corresponding channel and out of thecorresponding channel.

Of course, the inverter might be installed in a location where it is notor only partly subjected to radiation of the sun. This can be in ashaded place or an inside place.

According to one aspect a solar system is proposed for providingelectrical energy of predefined voltage and/or current comprising atleast one solar generator outputting electrical energy as a DC-signaland at least one inverter according to at least on aspect of the presentinvention for transforming the DC-signal of the solar generator into anAC-signal of predefined frequency for feeding into an isolated grid or apublic grid. A solar generator, comprising of one or a plurality ofphotovoltaic cells is usually installed in an area of increased sunradiation and thus an inverter coupled to this solar generator is alsosubjected to this increased sun radiation. To avoid overheating of theinverter, such solar system is provided with an inventive inverter, inparticular an inverter comprising a cover to protect the inverteragainst sun radiation. Such solar systems, in particular if they are oflarge size, are provided in rural areas or even deserts. Such solarsystems are more likely to be exposed to dust or other influences of theenvironment such as water. The reliability of such systems may beimproved by using an inverter having good cooling properties includinggood properties for protection against the sun, whereas at the same timeat least the main part of the inverter is effectively sealed againstdust and water and such alike.

BRIEF DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention are described with reference tothe accompanying figures, wherein

FIG. 1 shows a perspective view of a first embodiment of an inverteraccording to the invention,

FIG. 2 shows a front view of the embodiment according to FIG. 1,

FIG. 3 shows a back view of the embodiment of FIG. 1,

FIG. 4 is a cross sectional view of the embodiment of FIG. 3 accordingto the arrows A-A of FIG. 3,

FIG. 5 shows a cross sectional view of the embodiment of FIG. 3according is to the arrows B-B of FIG. 3, in greater detail and

FIG. 6 shows a bottom plan view of the embodiment of FIGS. 1-5.

FIG. 1 shows an inverter 1 having a cover 2. And according to theperspective of FIG. 1 the cover 2 basically completely covers theinverter 1, as the perspective according to FIG. 1 equals one possibledirection of the sun radiation. Attacked to the cover 2 is a display 4for displaying inverter related information. At the bottom of theinverter 1 there is also shown a drainage adapter 6. At the top and backedge of the inverter 1 there is indicated a common opening 8 for air toexit the inverter 1.

FIG. 2 also shows the cover 2, display 4 and the drainage adapter 6 ofthe inverter 1. In that front view a connector 10 is also indicated atthe bottom side of the inverter 1.

According to the back view of FIG. 3 only part of the cover 2 can beseen basically at both sides and at the top and the bottom of theinverter 1. Attached to the inverter 1 at its backside is a cover plate12 partly covering a heat sink 14 and thus forming a heat sink channel30 of a basically open configuration. It is to be noted, that the coverplate 12 covering the heat sink does not form part of the cover 2 forforming a cover channel. To blow air in an upward direction, two vents18 are positioned below the heat sink 14 and will, when in operation,blow air to the heat sink 14 and along the fin-like structure 20 of theheat sink.

FIG. 3 also shows in its bottom area a part of the back side of theinner housing 22. Attached to this inner housing are the vents 18 usingan attachment means 24. The back view according to FIG. 3 shows furtherconnectors 10 or connecting adapters for electrically connecting theinverter 1.

FIG. 4 shows a cross sectional view from a bottom perspective accordingto an intersection indicated by arrows A-A in FIG. 3. This viewillustrates the subdivision of the inverter 1. Accordingly, the inverter1 consists basically of an inner housing 22 enclosing electroniccomponents, a cover channel 28 defined between the cover 2 and the innerhousing 22 and a heat sink area or heat sink channel 30 basicallydefined between the inner housing 22 and a heat sink plate 12 and/or adevice such as a wall to which the inverter 1 is attached.

The inner housing 22 is sealed against the environment and a pressurecompensation adapter 32 is provided to fulfil a pressure equalisation ifnecessary. Accordingly, all electrical connections 10 (cf. FIG. 3 andFIG. 5) as well as connections 34 for proving a connection to chokespositioned on top of the inner housing 22 are adapted to ensure thesealed state of the inner housing 22.

The electronic components 26 are basically arranged on a main circuitboard 36, that is arranged in a plane parallel to a back wall 38 of theinner housing 22 but comprising a gap 40 between the main circuit board36 at the back wall 38. Many of the components 26 do not produceconsiderable heat and are arranged at the main circuit board 36 facingto the inside of the inner housing 22. Some of these components 26 arearranged on smaller circuit boards 27, which are attached or connectedto the main circuit board 36. It is to be noted, that the electroniccomponents 26, including the smaller circuit boards 27 are only shown ina schematic way and the components, the number of the components, thecertain arrangement and so on may vary with respect to differentinverters. However, the used electronic components and thus any possiblevariations are not of importance for the present invention.

The heat sink channel 30 is basically defined by the heat sink plate 12and/or a device such as a wall to which the inverter 1 is attached and asupport frame 13. The support frame 13 is attached to the inner housing22 at the back wall 38 and does support the heat sink 14. The heat sink14 comprises one base plate 42 and a plurality of fin-like means 44 forenlarging the surface of the heat sink 14. At the base plate 42 thereare provided protrusions 46, on which the heat sink 14 is attached tothe support frame 13 by means of screws 48.

The protrusions 46 function as distance pieces integrally formed withthe heat sink 14, to provide a gap 50 between the base plate 42 of theheat sink 14 and the support frame 13. Accordingly, a gap 50 is providedbetween the heat sink 14 and the inner housing 22. According to an otherembodiment, there are further fin-like means at the base plateprotruding into the gap, to further increase the surface of the heatsink.

According to FIG. 4, some power components 52, that need cooling duringoperation of the inverter 1 are mounted at the main circuit board 36,but face into the direction of the heat sink 14. These power components52 extend through the back wall 38 of the inner housing 22 to the baseplate 42 of the heat sink 14. These power components 52 are sealedagainst the back wall 38 of the inner housing 22. The power componentsare with one side attached to the base plate 42 of the heat sink 14such, that good heat conduction from the power components 52 to the heatsink 14 is provided. Accordingly, any heat conducting connection betweenthe inner housing and the heat sink 14 is only provided by means of thepower components 52 themselves. Such heat conducting connection isnecessary but any other heat conduction connections between the innerhousing and the heat sink are avoided. The gap 50 between the base plate42 of the heat sink 14 and the back wall 38 of the inner housing 22 alsoprovides for an air channel so air can flow through this gap and providefurther cooling for the heat sink as well as for the back wall 38 andthus for the inner housing 22.

A cover 2 is at two sides attached to the support frame 13 at attachmentlash 56 further involving support means 58. Because the cover 2 almosttouches edges 60 of the inner housing 22, the cover channel 28 isbasically subdivided in a front and two side cover channels 28 a-c. Acover channel 28 and also the sub channels 28 a-c according to FIG. 4provide a relatively large cross sectional area. Accordingly, there isno strong flow resistance hindering an upward air stream and thus thecover channel 28 and the sub channels 28 a-c provide for naturalconvection of air.

The cross sectional view according to FIG. 5 provides basically a sideperspective of the inverter 1. Accordingly, the vent 18 is arrangedbelow the heat sink 14 and adapted to provide an air stream having anupwards direction to flow along the heat sink 14. FIG. 5 also shows aslightly inclined position of the vent 18 and accordingly the vent 18ensures to also blow air into the gap 50 between the inner housing 22and the base plate 42 of the heat sink.

FIG. 5 more clearly shows some components of the inner housing 22, i.e.the drainage adapter 6, connectors 10 and electronic components 26 andsmaller circuit boards 27. Above the inner housing 22 a choke 54 ispositioned and connected via the connection 34 to the inner housing.

The cover 2, as seen in FIG. 5 comprises a front cover 62, a top cover64 and a bottom skirt 66. The top cover 64 completely covers the upperside of the inner housing 22 and the chokes 54 arranged above the innerhousing 22 at the top side. The cover 2 further provides a top opening68 of the cover channel 28. The air flowing upwards in the cover channel28 will thus exit the cover channel 28 at the top opening 68. It canalso be seen, that the choke 54 is basically positioned in the coverchannel 28 at one side of it. The top opening 68 thus basically faces ina backwards direction.

A bottom opening 70 for air to enter the cover channel 28 is basicallypositioned next to the bottoms skirt 66, facing in a downward direction.

FIG. 6 illustrates the shape of the skirt 66, basically forming a stripelike form according to the bottom view of this figure. This figure alsoshows the drainage adapter 6, connectors 10, vents 18 and a heat sink 14that is partly provided in a heat sink channel 30.

When operating the inverter 1 air in the cover channel 28 will be heatedin particular by means of the chokes 54 and by means of the cover 2 whenbeing heated by the sun. Accordingly, the heated air will flow upwardsaccording to natural convection and as a result cooler air from theoutside will flow into the bottom opening 70 and thus cool the innerhousing 22 and the cover 2 of the inverter, while gradually being heatedin the cover channel. The heated air flowing upwards will exit the coverchannel 28 at the top opening 68. For cooling the power components andthus cooling the heat sink 14, the vents 18 will blow air along the heatsinks 14, in particular along the fin-like means 44 and through the gap50 along the base plate 42. This air will be heated by the heat sink andwill be flowing in the heat sink channel. This hot air will exit theheat sink channel 30 in an area close to the top opening 68 of the coverchannel 28. In this area, the air of the cover channel 28 and the air ofthe heat sink channel 30 will come together. Because of the vents 18 theair in the heat sink channel usually has a larger velocity than the airin the cover channel 2, the air exiting the heat sink channel 30 mightprovide a suction effect on the air in the cover channel 22 and thusmight accelerate the air flow in the cover channel 28.

1. Inverter or other electronically controlled power source fortransforming electrical energy into electrical energy of predeterminedvoltage and/or current comprising: an inner housing for housing the maincircuitry of the inverter, and a cover connected to the inner housing,covering at least part of the inner housing, defining at least one coverchannel between the inner housing and the cover for air to flow throughthat channel for cooling of the inverter, whereby the cover channel isadapted to facilitate natural convection of the air.
 2. Inverteraccording to claim 1, whereby the cover channel is adapted to facilitatea vertically directed convection of air, when the inverter is arrangedin a normal up right operational position.
 3. Inverter according toclaim 1, whereby the cover channel has a basically vertical orientation,when the inverter is arranged in a normal up right operational position.4. Inverter according to claim 1, whereby the cover is adapted, toprotect the inner housing against sun light, in particular againstdirect radiation of sun light.
 5. Inverter according to claim 1, wherebythe cover comprises an outside having a light color, in particular whiteor silver.
 6. Inverter according to claim 1, whereby the cover covers atleast two sides of the inner housing, preferably at least three sidesand in particular five of six sides of the inner housing.
 7. Inverteraccording to claim 1, whereby at least one choke of the inverter orother component dissipating a high amount of energy, is positioned inthe channel such that air in the cover channel transports heat from thatchoke or other component and heat of that choke or other componentenhances convection of air in the channel.
 8. Inverter according toclaim 6, whereby the or a choke or other component dissipating a highamount of energy is positioned at the top and/or the bottom of the innerhousing.
 9. Inverter according to claim 1, whereby the cover channelcomprises an input opening for air to enter the cover channel and anoutput opening for air to exit the cover channel and whereby the inputopening is arranged at the bottom of the inverter and the output openingis arranged at the top of the inverter, when the inverter is arranged ina normal up right operational position.
 10. Inverter according to claim1, comprising: at least one heat sink for cooling power components ofthe inverter, whereby the heat sink is attached to the inner housing,basically providing a space between the heat sink and the inner housing.11. Inverter or other electronically controlled power source fortransforming electrical energy into electrical energy of predeterminedvoltage and/or current comprising: an inner housing for housing the maincircuitry of the inverter, at least one heat sink for cooling powercomponents of the inverter, whereby the heat sink is attached to theinner housing, basically providing a space between the heat sink and theinner housing.
 12. Inverter according to claim 1, whereby the innerhousing is sealed against the environment to protect the circuitry ofthe inverter against dust and/or water.
 13. Inverter according to claim10, whereby power components which need external cooling extend throughthe casing of the inner housing against the heat sink and are sealedagainst the inner housing.
 14. Inverter according to claim 10, wherebythe heat sink comprises a base plate having one or a plurality of powercomponents attached to that base plate, whereby the base plate comprisesprotrusions extending towards the power components so as to provide abase for each attached power component.
 15. Inverter according to claim10, whereby the heat sink is attached to the inner housing by means ofdistance pieces.
 16. Inverter according to claim 10, further comprisinga heat sink channel accommodating the heat sink for guiding air alongthe heat sink for cooling.
 17. Inverter according to claim 16, furthercomprising at least one vent for blowing air through the heat sinkchannel along the heat sink, in particular also through the spacebetween the inner housing and the heat sink.
 18. Inverter according toclaim 10, whereby an or the output opening of the cover channel isadjacent to an output opening of the heat sink channel.
 19. Method forsetting up and operating an inverter or other electronically controlledpower source for transforming electrical energy into electrical energyof predetermined voltage and/or current, having an inner housing forhousing the main circuitry of the inverter and a cover, covering atleast part of the inner housing, defining at least one cover channelbetween the inner housing and the cover comprising the steps: attachingthe inverter on an object such as a wall to hold the inverter, andarranging the cover channel in a basically vertical manner, such that aninput opening for air to enter the channel is basically arranged at thebottom of the channel and an output opening for air to exit the channelis basically arranged at the top of the channel.
 20. Method according toclaim 19, further comprising the step positioning the inverter such,that the cover basically faces the direction to the sun at day timesuch, that the cover at least partly protects the inner housing of theinverter against radiation of the sun at day time.
 21. Method accordingto claim 19, whereby at least one vent is driven to blow air along a orthe heat sink of the inverter and a flow of air is provided in the coverchannel by means of natural convection.
 22. Method according to claim19, whereby natural convection of air in the cover channel is enhancedby means of heat of at least one choke or other component dissipating ahigh amount of energy arranged in or at the cover channel.
 23. Solarsystem for providing electrical energy of predefined voltage and/orcurrent comprising at least one solar generator outputting electricalenergy as a DC-signal, and at least one inverter according to claim 1for transforming the DC-signal of the solar generator into an AC-signalof predefined frequency for feeding into a private grid or public grid.